Read the passage below. Use the information in the passage and your own knowledge
to answer the questions that follow.
Conditioned Reflexes
Humans respond to stimuli such as sound, sight, smell and taste. Sometimes the
response is a simple reflex. If we get a puff of air onto our eye, we blink. If we
touch a hot object with our fingertips, we pull our hand away.
Another type of reflex is a conditioned reflex. These were first described around
5 the beginning of the 20th century by the Russian physiologist Ivan Pavlov.
Pavlov was studying digestive processes in dogs when he discovered that the
dogs began to produce saliva before they received their food. In fact, after several
occasions of the lab assistants bringing the food, the dogs started to produce
saliva at the sight of the lab assistants. Pavlov called this ‘psychic secretion’.
10 He noted that dogs responded to a biological need (hunger) and also to a need
developed by learning.
To experiment on conditioned reflexes, Pavlov used a tuning fork that produced a
note of constant frequency. He hit the tuning fork and then gave the dog food.
In the beginning the dog produced saliva only when given the food. After the
15 combination of sound and then food were repeated, the dog produced saliva
at the sound of the tuning fork. Even when Pavlov took away the food, the dog
continued to produce saliva at the sound of the tuning fork alone. The dog
had learned to associate one stimulus with another. The dog learned that the
first stimulus is to be followed by the second stimulus. In Pavlov’s experiments,
20 first stimulus is to be followed by the second stimulus. In Pavlov’s experiments,
the sound of the tuning fork informed the dogs that food was coming. The
production of saliva was a conditioned reflex.
Pavlov then used a different tuning fork to produce a note of a different
frequency. He measured the size of the dog’s response to this note. He could
then compare this response to the dog’s response to the original tuning fork.
25 Many examples of conditioned reflexes exist in humans. Some psychologists
believe that phobias, such as the fear of spiders, may develop by associating a
neutral stimulus with a fearful one.